Before we kick off, the idea behind this build is making a simple SUP board that everybody can make. One of the things why i wanted to make a SUP unit is that not everybody has the sea near them for waves or lakes with big winds. So stand up paddleing is a lot more accesible as sports or activity than wave or wind surfing.

If you are interested in dimensioning and schematics I have a bundle of this project on my website:

www.seamm.nl

Step 1: Design

So the idea was a 'simple' SUP board. In general a surf board is fairly simple already. But my thought was let's keep it even simpler in design and design it so that it uses materials from the home center and keep exotics materials to a minimum.

So the first step was make it flat. I used two thin plywood sheets and keep those apart with EPS foam. The plywood was 6mm or 1/4 inch. And the foam was 3/4 inch or 70 mm. Because the plywood and foam were a sandwich the distance between the plywood sheets will give the board it's stiffness. And because the foam has a low density it gives the floating capacity.

These three parts are placed plainly on each other and in the middle of the board there is a 'rib' or 'upright' and the fin is in one piece with this upright.

EPS foam is a common material for surfboards, a usual alternative is PUR foam.

Step 2: Break Down the Plywood

So I used one standard sheet of plywood, 4 by 8 feet or 1220 by 2440 mm, it needed to be broken down. In my situation a circular handsaw was the best option. I used a large parallel guide, but a chalk or inkline will work fine. You can keep the saw in a straight enough line.

I used a jigsaw to remove material for the fin part. So you only need two saws for this project.

Step 3: Template

Both the sheets and the fin part are roughly sawn out. We can put the fin part away. I rolled out a long piece of paper over the sheets marked the centerline and stuck the paper to one half. when this was in position I determined the relevant 'points':

The widest point somewere half way.

The farthest point at the end of the fishtail.

And the setback point of the fishtail.

when those points were determined I drew a line as fluently as i could. ofcourse those line are not perfect but thats no big issue.

Step 4: Saw the Shape

When the lines are drawn and place on the plywood I clamped the sheets together and kept them firmly registered at the same spot. I sawed through both the sheets in one action with the jigsaw. And again that line was not as perfect as you would like it but that still does not matter.

after that the sheets still are in place and the edges are sanded, at this point the all the errors made in the line can be corrected until i am happy with the shape.

Before we can move on we need a thin mortice for the fin to pass through the bottom sheet. I simply made this with a few cuts of my chisel. A power router can work aswell, but that would take more time because you need set it up for a straight line.

Step 5: Glue Up!

By now the all wood has been processed.

For glueing the EPS and wood together I used polyurethane foam or PUR. This is a fairly cheap material with adequate strength, the strength difference between EPS and the PUR are unsignificant for this project.

The EPS sheets were glued staggered to keep the joints between the material to a minimum. I had to work quick because the foam sets up quick and it tries to push everything away from itself so when curing I placed weights on the assembly to correct this.

After assembly the excess foam can be trimmed away and I shaped it round with a rasp and course sandpaper.

Step 6: Epoxy

So one thing was inevitable; i had to use a thermoset resin (epoxy,polyester or polyurethane) to waterproof the whole thing. I chose Epoxy because its hard and strong and impermeable from wateringress. When the cups were mixed I mixed a small amount of sawdust in a small cup to fill up gaps from the assembly process.

Step 7: Glassfiber Lamination

So I enveloped the board in one layer of glassfiber and epoxy, this added strength and robustness. This keeps the sandwich construction from delamination.

I put on the epoxy first and then carefully dropped down the glassfiber from a roll above the board. after this it was impregnated and I worked out all the wrinkles and folds in the material.

Step 8: Sanding and the Next Layer

After the last step the epoxy has cured and i sanded the surface to a matte look and removed the sharp ends. it's wise to wear a respirator and protect your arms and hand from the sharp dust, you can get irritation from that.

So one side is done now the otherside can be laminated. I made a little extra epoxy/sawdust paste to place on the 'root' of the fin and laminated a layer of glass fiber on the the fin aswell. This makes the fin a bunch more rigid.

The front en and the points on the fishtail got one extra layer to make it more robust against dents and such.

Step 9: Eyenut

To be able to attach a cable or rope to the board; I threaded a long bolt through the complete assembly and screwed on a nut and eyenut. I used Loctite 243 to keep it in place. In my situation I used M6 thead, 1/4 Inch is a comparable size.

Step 10: Finish

After that I dusted off the board, outside my mini workshop. This saved my cleaning up the dust in the shop ;)

I used WD40 to make the surface look more even, because I used one layer of glassfiber the surface finish was a bit uneven. When you want to make it more fance you would add a layer or multiple layers of epoxy lacquer and make it look high gloss.

Most of my projects or objects are prototypes and I like to keep my processes quick so i chose not to tire myself with high gloss finishes. But if you can determine that for yourself :)

Step 11: Test!

So it turned out it's not easy to stay standing on a SUP board for the first time :p My nephews wanted to help me out with testing of the board and eventually we made it work and could stand and paddle.

Overall the board functions! it could be more stable if it was wider and for larger people it could be thicker but it still worked so i am happy this concept worked out!